1. Field of the Invention
The present invention relates generally to filters and, in particular, to improving responsiveness of a filter bank.
2. Description of the Background Art
Audio signal analysis typically uses a time-frequency analysis to extract a set of useful features or parameters. This can be accomplished through the use of a filter bank (i.e., an array) of band-pass filters to provide instantaneous spectra energy and phase measurements of an input signal. A digital filter bank is employed to separate the input signal into several components, each corresponding to a frequency sub-band filtered through by a corresponding band-pass filter of the filter bank. Such filter extraction is commonly used in a number of fields, including speech, radar, and sonar signal processing.
In an ideal (i.e., theoretical) filter bank, each filter has a boxcar frequency response, meaning that the filter's response is perfectly flat throughout its responsive range, with the response tapering off with infinite slope at the edge frequency or frequencies. Such an ideal filter bank is not physically realizable because the response to a step function input at a time t=0 would have to start prior to time t=0.
Accordingly, what is desired is a realizable filter bank that improves responsiveness across a particular frequency range.